Blown mineral wool insulation across South Glamorgan
We cover 3 towns in South Glamorgan: Cardiff, Barry and Penarth.
Every elevation is judged on its own exposure. Parts of South Glamorgan face some of the heaviest wind-driven rain in the UK, especially exposed coastal and upland sites. Here the survey is stricter: some walls suit only certain certified systems, and some should not be filled at all.
For semi-detached and terraced homes in South Glamorgan, cavity barriers are fitted where your wall meets your neighbour's so the fill stays on your side. South Glamorgan properties with rendered or painted walls get a closer look at the outer finish, because cracked render can let rain behind it.
Building Regulations in Wales
In Wales, filling an existing cavity is also notifiable building work under the Building Regulations as they apply in Wales. A registered installer normally self-certifies it through a competent person scheme; otherwise a building notice goes to your council's building control before work starts. Welsh rules can differ from England's, so the notification route is confirmed in writing on your quote.
Funding in Wales
- Warm Homes Nest offers free improvements, including insulation, to eligible low-income owner-occupiers and private renters; eligibility was widened to some households without means-tested benefits.
- Green Homes Wales has been piloting advice and interest-free loans for households above the Nest and ECO4 income thresholds.
- ECO4 runs until 31 December 2026 across Great Britain, including Wales.
Sources: Welsh Government: building work competent person schemes; CIGA: CWISC competent person scheme; Welsh Government: issues arising from cavity wall insulation installations; Welsh Government: warmer and more energy efficient homes (July 2026); GOV.UK: extending the ECO4 end date, government response.
Why choose mineral wool?
Mineral wool fibres are treated to shed water, so moisture that gets into the outer leaf runs down the cavity rather than tracking across. It is classed as non-combustible, which matters for some flats and taller buildings, and it is usually the lower-cost certified option.
It is installed at a set density through a regular drill pattern. Too loose and it settles; too tight and it can bridge moisture. That is why the installer's density checks and hole pattern are recorded on the job sheet.
What is included
- Certified mineral fibre system
- Density and drill pattern recorded
- Making good to the mortar colour
- Cavity barriers where needed
- Regulations route and guarantee named on the quote
Blown mineral wool insulation prices in South Glamorgan
| Blown mineral wool insulation guide prices | Guide price |
|---|---|
| Detached house | £1,895–£3,395 |
| Semi-detached house | £1,295–£2,195 |
| End-terrace house | £1,095–£1,895 |
| Detached bungalow | £1,095–£1,895 |
| Semi-detached bungalow | £795–£1,395 |
| Mid-terrace house | £795–£1,295 |
No VAT is charged on installing insulation in homes until 31 March 2027 (then 5%). Guide ranges only: the fixed price is confirmed in writing before any work starts, and anything that could not be seen at survey is agreed with you first.
The steps for blown mineral wool insulation in South Glamorgan:
Get in touch
Online, by phone or WhatsApp, whichever suits you.
Survey visit
The surveyor checks each wall and looks into the cavity where needed.
Your result in writing
What we found, what it means, and a fixed price if work is needed.
Booked work
Carried out by the installer named on your quote, with their scheme registrations.